Fusible link on a gas furnace?
Rather than put a fuse on this furnace, an old Day & Night,
the manufacturer stuck a small fusible link in the wire
just before the heat exhanger limit switch. I amp'ed the
line while the furnace was operating with the main
gas valve open, burners burning, and it was less than
1 amp. My first inclination is to put a 3 amp blade fuse
inline rather than order the fusible link.
Does doing so sound good or bad? The board has no
other fuse for control voltage. I jumped it out
with a 5 amp fuse and the furnace worked for three
heat cycle attempts with the above amperage.
Based on the above, I am inclined to believe the
fusible link failed rather than really prevent a
real high current hazard.
The furnace is old, rusty, and could otherwise use
replacement, but that isn't my decision.
it's called a fusible link for a reason
clue: it's not amperage
It`s better to be silent and thought the fool; than speak and remove all doubt.
I never ever, ever, modify a safety on a gas furnace........
Many manufactures use a fuse link......
I would take a long look at the heat exchanger......
"Value our Differences"
There are mechanical (heat sensitive) fusible links and
Originally Posted by dandyme
there are electrical fusible links. It is my belief, since this
is mounted about two inches from the surface of the
heat exchanger, that it is an electrical fusible link, hence
my reference to amperage. Thank you.
that fusible link is not a fuse! it is a safety for the heating cycle. figure out why it did its job. if you remove the link you are liable for the death that may occur
I believe you are confused about the function of a fusible link. They are designed to open on heat from a roll-out condition not high amperage. If you recall some of the older DNP products had 3 fuse links positioned on each side and above the heat exchanger opening. Probably not a bad idea to add a fuse to protect the system, now you must decide where is the best protection.
Originally Posted by georgelass
When the fusible link on DNP products opens it brings the blower on.
The reasons for continuous blower and no heat
1. open rollout or limit
2. bad transformer
3. fuse link
4. bad board
The reason the furnace came on after install fuse, you closed the circuit, but left out the safety device.
There are not three of these strategically located. This single one is merely
Originally Posted by mike3
inline with the wire to the limit switch. This particular one looks
most like a ceramic fusible link--actually, it looks like a resistor but
I don't have my notebook with me to look it up anywhere--and
all of the little ceramic fusible links I see online are rated by amperage,
not temperature. I'm open-minded to this, but the evidence seems
to point towards electrical protection, not temperature protection.
Thank you. I do appreciate your efforts. You are absolutely right--I
am confused, but I'm simply not yet convinced that it is about the
electrical versus temperature function of fusible links. I know there
are both kinds. I simply think this one is electrical.
something like this that hooks to the main hi limit right?
it is thermal protection.
carefully inspect HX and flue.
I believe, Trane uses a fuse link like Bro. George is talking about.....wish I had picture capabilities, I ordered three from Trane and got three boxes of 5......tried to send some back, but, they said it would be a hassele....lol...
They are the same size as a traditional limit or fan switch but have a one time fuse in them.....
Your furnace has issues.....
"Value our Differences"
Yes, that is roughly the same except it looks a lot newer and
I swear i did a forum search on fusible link before posting this
question but got nothing. But trying a google search, I found
this one post:
It certainly seems strange that it would be so far from the burners!
I've seen flames blow out enthusiastically from burners before and
they did not roll up the face of the heat exchanger. I suppose having
the doors off the unit changes the flames. That would make sense.
Thanks again to all who tried to help me see this, even those who
did not give much background! Sorry, but I'm from the Show-Me
state so I like some convincing.
i dont have pictures but, i got a service call about 3-4 years ago on a boiler. i turned the stat on. walked down to the basement turned the boiler switch on and watched it fireup and had all flames rolling out the heat exchanger and up the front of it. it melted the spark ignition box and wires but still fired up. it had no safeties. if there were a fuse link it would have shutdown the boiler
it is NOT electrical, but heat activated.
as has been stated, if it is bad, look for a flame issue!!!!!!!
Google search, http://www.google.com/search?q=day+a...ient=firefox-a, came up with this;
The Food Stamp Program, administered by the U.S. Department of Agriculture, is proud to be distributing the greatest amount of free meals and stamps EVER.
Meanwhile, the National Park Service, administered by the U.S. Department of the Interior, asks us to "Please Do Not Feed the Animals". Their stated reason for this policy "... the animals become dependent on handouts and will not learn to take care of themselves."
from an excerpt by Paul Jacob in Sun City, AZ